1. Field of the Invention
The invention pertains to a torsional vibration damper for a bridging clutch of a hydrodynamic clutch arrangement with a drive-side transmission element and a takeoff side transmission element, wherein the takeoff side element is rotatable by a limited amount relative to the drive side element under the action of energy storage devices.
2. Description of the Related Art
A torsional vibration damper assigned to the piston of a bridging clutch of a hydrodynamic clutch arrangement such as a torque converter, the damper being equipped with a drive-side transmission element attached to a piston of a bridging clutch, with an intermediate transmission element, and with a takeoff-side transmission element attached nonrotatably to a turbine wheel, is known from U.S. Pat. No. 5,941,354, where the drive-side transmission element and the takeoff-side transmission element position the intermediate element between them by means of a plurality of energy storage devices. According to FIG. 3, the intermediate element has not only openings for drive elements of both the drive-side transmission element and the takeoff-side transmission element but also its own drive element, which engages between two energy storage devices, where the openings of the intermediate element are larger in the circumferential direction than the associated drive element. As a result, a first stage of spring action is in effect in a first direction R1 of relative rotational deflection along a first travel path s1 until the drive element of the drive-side transmission element has used up the associated opening of the intermediate transmission element and comes into direct contact with a stop of the latter. When the relative rotational deflection between the two transmission elements becomes even larger, a second stage of spring action goes into effect under the effect of the drive element of the intermediate transmission element along a second travel path s2 until the intermediate transmission element has arrived in direct contact with a stop of the takeoff-side transmission element. In the opposite direction R2 of relative rotational deflection, this process takes place in a comparable manner, although, because the dimensions of the openings of the intermediate transmission element are different, different travel paths s1, s2 are predefined for the action of the individual spring stages. As a result, the torsional vibration damper operates differently during phases in pull mode than it does during phases in push mode. In sum, because there are two different stages of spring action in each of the two directions R1, R2 of relative rotational deflection, what is obtained is a low degree of spring stiffness at small relative rotational deflections and a high degree of spring stiffness at large relative rotational deflections.
Although it is possible with this torsional vibration damper to adapt the spring stiffness with considerable sensitivity to the degree of relative rotational deflection between the two transmission elements and also to adapt that stiffness optimally to operational phases in pull and push mode, energy storage devices are used which are very long in the circumferential direction, for which reason these devices must be guided along their entire radially outer circumferential dimension by suitable circumferential supports in such a way that they can resist the action of the centrifugal forces caused by the rotation of the damper. Nevertheless, under the action of centrifugal force, strong frictional forces develop between the individual turns of the spring and the circumferential support, and, as the degree of the relative rotational deflection of the transmission elements increases, these forces lead to a considerable reduction in the ability of the energy storage devices to deform and, as a result, to a considerable deterioration in the quality with which vibrations can be isolated. The energy storage devices which are situated in the radially outer area and thus have considerable length in the circumferential direction, furthermore, require a great deal of work to manufacture and are therefore expensive.
A torsional vibration damper of simpler design and lower cost is known from U.S. Pat. No. 5,810,138, which discloses a drive-side transmission element, a takeoff-side transmission element, and energy storage devices installed functionally between them. This torsional vibration damper, too, is assigned to the piston of a bridging clutch of a hydrodynamic clutch arrangement such as a torque converter and is for this purpose connected nonrotatably by its drive-side transmission element to the piston of the bridging clutch, whereas the takeoff-side transmission element is attached to a sleeve connected nonrotatably to a gearbox input shaft.
The energy storage devices in this torsional vibration damper are arranged in specially provided openings in the transmission elements and are thus located on a relatively small radius around the axis of rotation. As a result, the energy storage devices are very short in the circumferential direction, so that, under the action of centrifugal force, they are bent radially outward to only a very limited extent. Nevertheless, this torsional vibration damper, regardless of the angle of relative rotational deflection at the moment in question, can react only with the one stage of spring action, nor does it have the capacity to operate under push-mode conditions differently than it does under pull-mode conditions. It is therefore to be considered especially suitable for small torsional vibration dampers with only moderate vibrational isolation quality.